The present invention relates to a power supply device and power control method and, more particularly, to a power supply for supplying electric power to an electronic device such as a printer or the like, and a power control method.
While an electronic device such as a printer or the like, which operates upon receiving electric power supplied from a commercial power supply line, is not in use, it is a common practice to stop power supply from the power supply line.
In recent years, as the functions and precision of such apparatuses have been improving, a series of operations have been required for protecting electronic circuits of the respective units of the apparatus and for preparing for switching these circuits from their enable status before power supply to such apparatus is stopped (before the apparatus goes to a power OFF state). Hence, such an apparatus is required to go to an actual power OFF state after a series of protection operations upon receiving a power OFF instruction.
In addition, since a motor circuit or the like of the printer need not receive any electric power in the power OFF state, power supply to that circuit can be stopped. However, a control circuit that controls processes of the overall apparatus is required to operate even in the power OFF state for the purpose of monitoring the next power ON instruction, supervising time, and so forth, and power supply to the control circuit cannot be completely shut off in many cases.
Therefore, in order to reduce consumption power while the apparatus is not in use, measures for lowering the operation clock frequency of such control circuit, operating a CPU in a sleep mode, and so forth are taken.
However, although the consumption power is expected to reduce since the load current is reduced, when the size of the control circuit itself of the apparatus is large, the number of elements that require power supply increases, and electric power required for driving such elements increases in proportion to the circuit scale. For this reason, when consumption power while the apparatus is not in use is reduced to a given value or less, the circuit scale of the control circuit must also be limited to a given scale or less.
To solve this problem, a circuit which is not required for actual operations such as a special switch or the like for shutting off power supply to circuits except for elements to which minimum required electric power must be kept supplied must be added.
Accordingly, it is an object of the present invention to provide a power supply apparatus and power control method, which can reduce consumption power while an electronic device such as a printer is not in use irrespective of the scale of a control circuit of that apparatus.
According to one aspect of the present invention, the foregoing object is attained by providing a power supply apparatus which comprises a power supply unit for supplying electric power to an electronic device in accordance with an instruction from a power switch, comprising detection means for detecting an ON/OFF instruction to the power switch, power supply means for supplying electric power to the detection means even after the OFF instruction to the power switch is detected, and control means for controlling to stop power supply from the power supply unit to the electronic device when the OFF instruction to the power switch is detected.
Note that the power supply means may be a battery.
As the electronic device, for example, a printing apparatus may be used, and the printing apparatus may include a timer circuit, which operates upon receiving electric power from the battery.
In such arrangement, the printing apparatus writes a time at an OFF instruction timing of the power switch into a nonvolatile memory, and when an ON instruction to the power switch is detected, and the printing apparatus becomes enabled later, the printing apparatus reads time information from the timer circuit, and executes a predetermined operation upon power ON on the basis of the read time information and the time written into the nonvolatile memory.
The power supply means may use a part of an output from the power supply unit. In this case, the power supply unit has, as an operation mode, a first operation mode for supplying electric power to the electronic device, and a second operation mode for supplying electric power to only the power supply means, and the control means switches the operation mode of the power supply unit in accordance with a detection result of the detection means. For example, when the OFF instruction to the power switch is detected, the control means switches the power supply unit to the second mode.
According to another aspect of the present invention, the foregoing object is attained by providing a method of controlling power supply to an electronic device in accordance with an instruction from a power switch, comprising: a detection step of detecting an ON/OFF instruction to the power switch by a detector; a power supply step of supplying electric power to the detector even after the OFF instruction to the power switch is detected; and a control step of controlling to stop power supply from the power supply to the electronic device when the OFF instruction to the power switch is detected.
In accordance with the present invention as described above, electric power is supplied to the detection means which detects an ON/OFF instruction to the power switch that supplies electric power from the power supply circuit to the electronic device even after the OFF instruction to that power switch is issued, and after a series of power-OFF sequences are performed, control is made to stop power supply from the power supply circuit to the electronic device.
The invention is particularly advantageous since electric power is supplied to only the detection means which detects an ON/OFF instruction to the power switch after the OFF instruction of the power switch is issued, and consumption power during power OFF can be reduced irrespective of the circuit scale of the electronic device to which electric power is supplied.
Also, since no special switch for reducing consumption power need be added, the cost of the apparatus can be prevented from increasing.